Microdevices are manufactured by depositing and working several layers of materials on a single substrate to produce a large number of individual devices. For example, layers of photoresist, conductive materials, and dielectric materials are deposited, patterned, developed, etched, planarized, and so forth to form features in and/or on a substrate. The features are arranged to form integrated circuits, micro-fluidic systems, and other structures.
Wet chemical processes are commonly used to form features on microfeature workpieces. Wet chemical processes are generally performed in wet chemical processing tools that have a plurality of individual processing chambers for cleaning, etching, electrochemically depositing materials, or performing combinations of these processes. In some cases, the processing chambers include a vessel configured to electrolytically apply material to the workpiece and/or remove material from the workpiece. The workpiece is partially immersed in a bath that includes an electrolyte in fluid communication with an electrode. When material is to be added to the workpiece, electrical potentials of opposite polarities are applied to the electrode (which functions as an anode) and the workpiece (which functions as a cathode). When material is to be removed from the workpiece, the polarities are reversed so that the electrode operates as a cathode and the workpiece operates as an anode.
During electrolytic processing, a diffusion layer develops at the surface of the workpiece in contact with the electrolytic liquid. The concentration of the material applied to or removed from the workpiece varies over the thickness of the diffusion layer. In many cases, it is desirable to reduce the thickness of the diffusion layer so as to allow an increase in the speed with which material is added to or removed from the workpiece. In other cases, it is desirable to otherwise control the material transfer at the surface of the workpiece, for example to control the composition of an alloy deposited on the surface, or to more uniformly deposit materials in surface recesses having different aspect ratios.
One approach to reducing the diffusion layer thickness is to increase the flow velocity of the electrolyte at the surface of the workpiece. For example, some vessels include paddles that translate or rotate immediately adjacent to the workpiece to create a high speed, agitated flow at the surface of the workpiece. In other arrangements, fluid jets are directed at the workpiece to agitate the flow at the workpiece surface.
The foregoing arrangements suffer from several drawbacks. For example, the electrode may not apply or remove material from the workpiece in a spatially uniform manner, causing some areas of the workpiece to gain or lose material at a greater rate than others. Existing devices are also not configured to transfer material to and/or from different types of workpieces without requiring lengthy, unproductive time intervals between processing periods, during which the devices must be reconfigured (for example, by moving the electrodes and/or a shield to adjust the electric field within the electrolyte). Another drawback is that the paddles can disturb the uniformity of the electric field created by the electrode, which further affects the uniformity with which material is applied to or removed from the workpiece. Still another drawback with the foregoing arrangements is that the vessel may also include a magnet positioned proximate to the workpiece to control the orientation of material applied to the workpiece. When the electrode is removed from the vessel for servicing or replacement, it has been difficult to do so without interfering with and/or damaging the magnet.